The present invention relates to a hydrogen supply system for a fuel cell, and a method for recycling a fuel and a system for recycling the fuel for the hydrogen supply system.
Fuel cells have a high energy efficiency and can readily be miniaturized. Therefore, fuel cells have been employed as a power source for electric cars. Particularly, a solid polymer fuel cell is advantageous as a power source for automobiles and household power plants since the operation temperature thereof is relatively low (100xc2x0 C. or less).
In one type of fuel cell, electromotive force is produced by a reaction that forms water from hydrogen and oxygen. This reaction requires a hydrogen supply system for supplying hydrogen to the fuel cell.
A fuel cell for an automobile is preferably light and small. A heavy fuel cell deteriorates fuel consumption, and a large fuel cell is disadvantageous in that it is difficult to design the location of a vehicle on which the fuel cell is mounted. Thus, a hydrogen supply system that is small, light, and can supply hydrogen in an amount sufficient for running over a long distance is needed.
Generally, for increasing the power generation efficiency of a fuel cell, it is preferred to employ a method of supplying pure hydrogen to the fuel cell. Known methods for supplying pure hydrogen include using high pressure hydrogen gas stored in a gas tank (high pressure gas mode), using hydrogen absorbed in a metal alloy having hydrogen absorbed therein (hydrogen absorption metal alloy mode), using the liquid hydrogen stored in a heat insulating tank (liquid hydrogen mode), and supplying a mixed gas of hydrogen and carbon dioxide gas obtained by reforming a hydrocarbon compound, such as methane, methanol or the like.
However, the high pressure gas method is too large. In the liquid hydrogen method, a gasifying loss occurs, and a great amount of energy is required for liquefying hydrogen, and thus, the overall efficiency is low. The hydrogen absorption metal alloy method requires an alloy 50 times or more heavier than the weight of hydrogen to be supplied. Therefore, the weight of the system is too high. The high pressure gas method and the hydrogen absorption metal alloy method require equipment for supplying hydrogen. On the other hand, liquid hydrogen is difficult to handle because it is cryogenic. Developments of methods and apparatuses for automatically supplying liquid hydrogen are progressing; however, an infrastructure will be required.
A hydrogen supply system in which hydrogen is formed by reforming a hydrocarbon compound, such as methanol, gasoline or the like, is now being developed. The reformation of a hydrocarbon compound uses a liquid organic compound as a fuel, which is easy to handle.
The methanol reformation method includes a steam reformation method, a partial oxidation reformation method, and an auto-thermal method, in which the thermal balance is maintained by combining the above two modes. The reaction formulae are as follows.
Steam reformation: CH3OH+H2Oxe2x86x923H2+CO2 
Partial oxidation reformation: CH3OH+1/2O2xe2x86x922H2+CO2 
However, in each of the above reactions, carbon in the hydrocarbon compound (methanol) is discharged into air as CO2. Therefore, these methods are not favored from the viewpoint of preventing global warming.
Further, the power generation efficiency of fuel cells is generally about 50%, and the remaining 50% becomes waste heat. For protecting the solid polymer electrolyte membrane used in the fuel cell from the heat of reaction during power generation, it is necessary to discharge the reaction heat efficiently. Conventionally, a fuel cell is cooled by a cooling apparatus having a radiator, which maintains the operation temperature at 100xc2x0 C. or lower. In this cooling apparatus, the heat of the fuel cell is transferred from the radiator with cooling water. However, since the difference between the temperature of the cooling water (e.g., 60 to 80xc2x0 C.) discharged and the external environmental temperature (e.g., 30xc2x0 C.) around the radiator is small, the heat dissipation efficiency of the radiator was poor. For this reason, a fuel cell system typically includes a large radiator having a large heat dissipation area, and as a result, the fuel cell system is large.
The first object of the present invention is to provide a hydrogen supply system for use in a fuel cell, which is advantageous in that it is relatively small, can supply pure hydrogen to the fuel cell, and discharges almost no carbon dioxide gas. Also provided is a system for recycling the fuel used by a fuel cell system. The second object of the present invention is to reduce the size of the fuel cell system.
To achieve the above object, the present invention provides a hydrogen supply system for supplying hydrogen to a fuel cell. The hydrogen supply system has a fuel chamber for storing a liquid fuel, which includes a hydrogen containing organic compound, a dehydrogenation apparatus for dehydrogenating the fuel to form hydrogen gas and a by-product, a gas-liquid separation apparatus for separating the hydrogen gas from the by-product by liquefying the by-product and for supplying the separated hydrogen gas to the fuel cell, and a recovery chamber for recovering and storing the by-product liquefied in the gas-liquid separation apparatus.
A further aspect of the present invention provides a method for recycling a fuel used in a hydrogen supply system for a fuel cell. The fuel cell and the hydrogen supply system are placed at a first region. The hydrogen supply system has a fuel chamber for storing a liquid fuel, which includes an organic compound containing hydrogen, a dehydrogenation apparatus for dehydrogenating the fuel to form hydrogen gas and a by-product, a gas-liquid separation apparatus for liquefying the by-product to separate the hydrogen gas from the by-product, and a recovery chamber for recovering and storing the by-product. The separated hydrogen gas is supplied to the fuel cell. The method includes a first transportation step for transporting the by-product from the first region to a second region, which is different from the first region, using a first mobile tanker, a regeneration step for regenerating the fuel by hydrogenating the by-product in the second region, and a second transportation step for transporting the fuel regenerated to refueling equipment placed at the first region using a second mobile tanker.
Another aspect of the present invention provides a refueling equipment for storing a fuel used in a hydrogen supply system for use in a fuel cell. The hydrogen supply system has a fuel chamber of the hydrogen supply system for storing a liquid fuel, which includes an organic compound containing hydrogen, a dehydrogenation apparatus for dehydrogenating the fuel to form hydrogen gas and a by-product, a gas-liquid separation apparatus for liquefying the by-product to separate the hydrogen gas from the by-product, and a recovery chamber of the hydrogen supply system for recovering and storing the by-product in the gas-liquid separation apparatus. The separated hydrogen-gas is supplied to the fuel cell. The refueling equipment includes a fuel chamber of the refueling equipment for storing a fuel used in the hydrogen supply system, a recovery chamber of the refueling equipment for recovering and storing the by-product in the recovery chamber of the hydrogen supply system, and a movable partition for separating the fuel chamber of the refueling equipment and the recovery chamber of the refueling equipment, wherein the movable partition changes the volume of the fuel chamber of the refueling equipment and the volume of the recovery chamber of the refueling equipment by moving depending on the liquid amount in the fuel chamber of the refueling equipment and the liquid amount in the recovery chamber of the refueling equipment.
Another aspect of the present invention provides a mobile tanker. The mobile tanker has a fuel cell, a hydrogen supply system for supplying hydrogen to the fuel cell, an electric actuator driven by the fuel cell, and a tank, and moves by the electric actuator. The hydrogen supply system has a dehydrogenation apparatus for forming hydrogen gas and a by-product from a liquid fuel, which comprises an organic compound containing hydrogen, and a gas-liquid separation apparatus for liquefying the by-product to separate the hydrogen gas from the by-product, and the separated hydrogen gas being supplied to the fuel cell. The tank includes a tank fuel chamber for containing and transporting the fuel for the hydrogen supply system and the mobile tanker, a tank recovery chamber for recovering and storing the by-product from the gas-liquid separation apparatus, and a movable partition for separating the tank fuel chamber and the tank recovery chamber. The movable partition changes the volume of the tank fuel chamber and the volume of the tank recovery chamber by moving depending on the liquid amount in the tank fuel chamber and the liquid amount in the tank recovery chamber.
A further aspect of the present invention provides a system for recycling a fuel for use in a fuel cell. The recycling system includes a vehicle having a fuel cell and a hydrogen supply system for supplying hydrogen to the fuel cell, external recovery means for recovering the by-product from the recovery chamber into an external recovery tank, fuel regeneration means for hydrogenating the by-product in the external recovery tank to regenerate the fuel, and refueling means for supplying the fuel regenerated to the vehicle. The hydrogen supply system has a dehydrogenation apparatus for forming hydrogen gas and a by-product from a liquid fuel, which includes an organic compound containing hydrogen, a gas-liquid separation apparatus for liquefying the by-product to separate the hydrogen gas from the by-product, and a recovery chamber for recovering and storing the by-product in the gas-liquid separation apparatus.
A further aspect of the present invention provides a vehicle having a fuel cell and a hydrogen supply system for supplying hydrogen to the fuel cell. The hydrogen supply system includes a dehydrogenation apparatus for forming hydrogen gas and a by-product from a liquid fuel that includes a hydrogen-containing organic compound, a gas-liquid separation apparatus for separating the hydrogen gas from the by-product by liquefying the by-product and for supplying the separated hydrogen gas to the fuel cell, and a recovery chamber for recovering and storing the by-product liquified in the gas-liquid separation apparatus.
A further aspect of the present invention provides a household power plant having a fuel cell and a hydrogen supply system for supplying hydrogen to the fuel cell. The hydrogen supply system includes a dehydrogenation apparatus for forming hydrogen gas and a by-product from a liquid fuel including a hydrogen-containing organic compound, a gas-liquid separation apparatus for separating the hydrogen gas from the by-product by liquefying the by-product and for supplying the separated hydrogen gas to the fuel cell, and a recovery chamber for recovering and storing the by-product liquified in the gas-liquid separation apparatus.
Other aspects and advantages of the present invention will become apparent from the following description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention.